Regulations governing exhaust emissions from internal combustion engines are becoming increasingly more stringent in many jurisdictions. Among the regulated exhaust emissions are NOx, particulate matter and hydrocarbons. Many machines utilize internal combustion engines as a means of powering propulsion systems, work implements and the like. Among these machines are track-type tractors, wheel loaders, compactors, excavators, graders, forestry machines, scrapers, and many others. While great strides have been made in reducing undesirable engine exhaust emissions at the point of combustion using a variety of innovative techniques, it may still be necessary to treat engine exhaust before venting via a tail pipe to the atmosphere, in order to meet regulation requirements. Most machines have evolved to design shapes that best facilitate their specific purpose. As a consequence, limited spatial envelopes are available for the incorporation of exhaust aftertreatment devices, without requiring substantial and costly redesign of the machine. These spatial envelope constraints may be further acute by other requirements, such as maintaining heat rejection levels from an engine or other components at satisfactory levels.
In one specific example, track-type tractors include a diesel engine mounted on a frame within an engine compartment that is covered by an engine hood assembly. In the case of the Caterpillar D10 track-type tractor, a portion of the muffler assembly for the exhaust may be incorporated into the engine hood. While this strategy better integrates noise suppression mufflers into the overall machine design, it fails to account for a more current need to treat exhaust for more than noise emissions. In particular, the current D10 tractor has limited space available for incorporation of exhaust aftertreatment devices while maintaining heat rejection standards for the engine and maintaining other requirements, such as operator visibility.
The present disclosure is directed toward one or more of the problems set forth above.